U.S. patent number 10,351,742 [Application Number 15/543,060] was granted by the patent office on 2019-07-16 for silicone pressure sensitive adhesives.
This patent grant is currently assigned to DOW SILICONES CORPORATION. The grantee listed for this patent is Dow Corning Corporation. Invention is credited to Janelle L. Brown, Julie Lyn Cook, Leon Neal Cook, Elizabeth Kelley, Timothy Paul Mitchell, Lori Jean Sutton, Stephanie Thompson.
United States Patent |
10,351,742 |
Brown , et al. |
July 16, 2019 |
Silicone pressure sensitive adhesives
Abstract
The invention provides a process for the production of a
pressure sensitive adhesive, comprising dissolving a particulate
solid MQ silicone resin having a bulk density in the range 0.4-0.9
g/cm.sup.3 in a volatile solvent, and dissolving a
polydiorganosiloxane having a viscosity of 0.1 to 40,000 Pas at
25.degree. C. in the volatile solvent before, simultaneously with
or after dissolving the solid MQ silicone resin. The process of the
present invention allows the production of a pressure sensitive
adhesive in a solvent different from the solvent in which the MQ
silicone resin was prepared.
Inventors: |
Brown; Janelle L. (Beaverton,
MI), Cook; Julie Lyn (Turner, MI), Cook; Leon Neal
(Midland, MI), Kelley; Elizabeth (Hope, MI), Mitchell;
Timothy Paul (Clio, MI), Sutton; Lori Jean (Saginaw,
MI), Thompson; Stephanie (Boyne City, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Corning Corporation |
Midland |
MI |
US |
|
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Assignee: |
DOW SILICONES CORPORATION
(Midland, MI)
|
Family
ID: |
55353293 |
Appl.
No.: |
15/543,060 |
Filed: |
January 19, 2016 |
PCT
Filed: |
January 19, 2016 |
PCT No.: |
PCT/US2016/013839 |
371(c)(1),(2),(4) Date: |
July 12, 2017 |
PCT
Pub. No.: |
WO2016/118472 |
PCT
Pub. Date: |
July 28, 2016 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
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US 20180044566 A1 |
Feb 15, 2018 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62105307 |
Jan 20, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L
83/00 (20130101); C09J 183/08 (20130101); C09J
183/04 (20130101); C09J 183/06 (20130101); C09J
183/04 (20130101); C08L 83/00 (20130101); C09J
183/06 (20130101); C08L 83/00 (20130101); C09J
183/08 (20130101); C08L 83/00 (20130101); C08G
77/04 (20130101); C08G 77/16 (20130101); C08G
77/70 (20130101); C08G 77/20 (20130101) |
Current International
Class: |
C09J
183/06 (20060101); C09J 183/04 (20060101); C08L
83/00 (20060101); C09J 183/08 (20060101); C08G
77/00 (20060101); C08G 77/04 (20060101); C08G
77/16 (20060101); C08G 77/20 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
PCT/US2016/013839 International Search Report dated Apr. 21, 2016,
3 pages. cited by applicant.
|
Primary Examiner: Harlan; Robert D.
Attorney, Agent or Firm: Warner Norcross & Judd LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the National Stage of International Application
No. PCT/US2016/013839 filed on 19 Jan. 2016, which claims priority
to and all advantages of U.S. Appl. No. 62/105,307 filed on 20 Jan.
2015, the content of which is hereby incorporated by reference.
Claims
The invention claimed is:
1. A process for the production of a pressure sensitive adhesive,
the process comprising: feeding at least one MQ silicone resin
dispersed in a volatile solvent into an extruder; removing the
volatile solvent in the extruder to form a solid solventless MQ
silicone resin; extruding the solid solventless MQ silicone resin;
comminuting the extruded solid solventless MQ silicone resin to
produce a particulate solid MQ silicone resin having a bulk density
in the range of 0.4 to 0.9 g/cm.sup.3; dissolving the particulate
solid MQ silicone resin in a volatile solvent; and dissolving a
polydiorganosiloxane having a viscosity of from 0.1 to 40,000 Pas
at 25.degree. C. in the volatile solvent before, simultaneously
with or after dissolving the particulate solid MQ silicone resin in
the volatile solvent.
2. The process according to claim 1, wherein the MQ silicone resin
has the general formula
R.sup.1.sub.n(R.sup.2O).sub.bSiO.sub.(4-n-b/2), where each R.sup.1
is monovalent and independently selected from hydrogen, alkyl,
alkenyl, oximo, aryl, carbinol, anhydride, epoxy, carboxyl, ether,
polyether, amide, and alkyl amino groups, which R.sup.1 groups may
be the same or different, with the proviso that at least 60 mole
percent of R.sup.1 groups are methyl, each R.sup.2 is hydrogen or a
monovalent alkyl group having 1 to 4 carbon atoms, n has an average
value from 1.1 to 1.6, and b is such that group (R.sup.2O) is 0 to
10 weight percent of the MQ silicone resin.
3. The process according to claim 1, wherein the MQ silicone resin
has a number average molecular weight (Mn) between 1,500 and
30,000.
4. The process according to claim 1, wherein the volatile solvent
into which the particulate solid MQ silicone resin and
polydiorganosiloxane are dissolved comprises at least one aliphatic
hydrocarbon having 6 to 16 carbon atoms.
5. The process according to claim 1, wherein the volatile solvent
into which the particulate solid MQ silicone resin and
polydiorganosiloxane are dissolved comprises at least one volatile
silicone solvent selected from trimethylsilyl-terminated
polydimethylsiloxanes having a viscosity of from 0.65 to 5 mPas at
25.degree. C., cyclic polydimethylsiloxanes, and 3-octyl
heptamethyl trisiloxane.
6. The process according to claim 1, wherein the volatile solvent
into which the particulate solid MQ silicone resin and
polydiorganosiloxane are dissolved comprises toluene or xylene.
7. The process according to claim 1, wherein the volatile solvent
into which the particulate solid MQ silicone resin and
polydiorganosiloxane are dissolved comprises at least one C.sub.1-8
alkyl ester of a C.sub.2-4 carboxylic acid.
8. The process according to claim 1, wherein the
polydiorganosiloxane contains groups reactive with groups present
in the MQ silicone resin.
9. The process according to claim 8, wherein the
polydiorganosiloxane is a hydroxyl-terminated polydiorganosiloxane
and the MQ silicone resin has the general formula
R.sup.1.sub.n(R.sup.2O).sub.bSiO.sub.(4-n-b/2), where each R.sup.1
is monovalent and independently selected from hydrogen, alkyl,
alkenyl, oximo, aryl, carbinol, anhydride, epoxy, carboxyl, ether,
polyether, amide, and alkyl amino groups, which R.sup.1 groups may
be the same or different, with the proviso that at least 60 mole
percent of R.sup.1 groups are methyl, each R.sup.2 is hydrogen or a
monovalent alkyl group having 1 to 4 carbon atoms, n has an average
value from 1.1 to 1.6, and b is such that group (R.sup.2O) is 1 to
10 weight percent of the MQ silicone resin.
10. The process according to claim 9, wherein a catalyst for
condensation of the polydiorganosiloxane and the MQ silicone resin
is dissolved in the volatile solvent before, simultaneously with or
after dissolving the solid MQ silicone resin.
11. The process according to claim 10, wherein the catalyst is
selected from carboxylic acids and metal salts of carboxylic
acids.
12. The process according to claim 10, wherein the catalyst is a
base selected from alkali metal oxides, alkali metal alkoxides,
alkali metal hydroxides, alkali metal silanolates, alkali metal
siloxanolates, alkali metal amides, alkyl metals, ammonia, amines
and ammonium hydroxide.
13. The process according to claim 10, further comprising heating
the solution of the MQ silicone resin, the polydiorganosiloxane and
the catalyst for condensation of the polydiorganosiloxane and the
MQ silicone resin at a temperature in the range of 50.degree. C. to
200.degree. C.
14. The process according to claim 8, wherein the
polydiorganosiloxane is an alkenyl-functional polydiorganosiloxane,
and a Si-H functional polysiloxane crosslinking agent and a
hydrosilylation catalyst are dissolved in the volatile solvent
before, simultaneously with or after dissolving the solid MQ
silicone resin.
15. The process according to claim 1, wherein the weight ratio of
the solid MQ silicone resin to polydiorganosiloxane is in the range
of 0.5:1 to 4:1.
16. The process according to claim 1, wherein a portion of the
polydiorganosiloxane is added to the MQ silicone resin in the
extruder, so that the particulate solid MQ silicone resin produced
by comminuting the extruded solid solventless MQ silicone resin
contains a minor proportion of the polydiorganosiloxane.
17. The process according to claim 16, wherein the weight ratio of
the MQ silicone resin to polydiorganosiloxane in the particulate
solid MQ silicone resin is in the range of 5:1 to 50:1.
Description
FIELD OF THE INVENTION
This invention relates to silicone pressure sensitive adhesives and
to their production.
BACKGROUND OF THE INVENTION
Many silicone pressure sensitive adhesives are produced by mixing a
solution of a branched silicone resin, specifically an MQ silicone
resin with a polydiorganosiloxane and optionally a catalyst for
condensation of the polydiorganosiloxane with the MQ silicone resin
and/or a crosslinking agent for the polydiorganosiloxane.
By a `MQ silicone resin` we mean a polymer comprised primarily of
R.sub.3SiO.sub.1/2 and SiO.sub.4/2 units (the M and Q units,
respectively) wherein R is a functional or non-functional,
substituted or unsubstituted monovalent radical. The MQ silicone
resin may also include a limited number of R.sub.2SiO.sub.2/2 and
RSiO.sub.3/2 units, respectively referred to as D and T units. As
used herein, the term "MQ silicone resin" means that, on average,
no more than about 20 mole percent of the resin molecules are
comprised of D and T units.
A siloxane is a compound which contains at least one Si--O bond. A
polysiloxane is a compound containing several Si--O--Si-- bonds
forming a polymeric chain, where the repeating unit is --(Si--O)--.
An organopolysiloxane is sometimes called a silicone. An
organopolysiloxane contains repeating --(Si--O)-- units where at
least one Si atom bears at least one organic group. "Organic" means
containing at least one carbon atom. An organic group is a chemical
group comprising at least one carbon atom. A "silicone resin" or
"resin" is a silicone comprising T and/or Q units.
MQ silicone resins are generally prepared in solution in an
aromatic hydrocarbon solvent such as xylene or toluene, and are
usually sold as solutions in the aromatic hydrocarbon solvent in
which they were prepared. Thus silicone pressure sensitive
adhesives are produced by dissolving a polydiorganosiloxane in a
solution of a MQ silicone resin in an aromatic hydrocarbon
solvent.
For some uses the solvent in which the MQ silicone resin was
prepared is not a suitable vehicle for a pressure sensitive
adhesive for that particular use. The process of the present
invention allows the production of a pressure sensitive adhesive in
a solvent different from the solvent in which the MQ silicone resin
was prepared.
U.S. Pat. No. 5,726,256 describes producing a pressure sensitive
adhesive by mixing a solution of a MQ silicone resin with a
polydiorganosiloxane and an acid catalyst and reacting the MQ
silicone resin with the polydiorganosiloxane. Reaction of
polydiorganosiloxane with MQ silicone resin is typically called
"bodying." U.S. Pat. No. 5,861,472 describes producing a `bodied`
pressure sensitive adhesive from a solution of a MQ silicone resin,
a polydiorganosiloxane and a base catalyst. WO2007/067332 describes
a continuous method for preparing a pressure sensitive adhesive by
mixing a hydroxyl-functional polydiorganosiloxane polymer, a
hydroxyl-functional polyorganosiloxane resin and a solvent while
heating the composition at a temperature above the vaporization
point of the solvent and removing volatile species in a
devolatilizing twin-screw extruder.
U.S. Pat. No. 5,324,806 describes forming a free flowing silicone
powder having a primary particle size in the range of 0.1-200 nm
and an aggregate size of 10 nm to 200 microns by spray drying an
organic solvent dispersion of a MQ resin. U.S. Pat. No. 5,319,040
describes capping such MQ resin by reaction with an organosilicon
nitrogen material, for example a silazane, before spray drying.
Either type of spray dried MQ resin can be used to make heat
curable organopolysiloxane compositions, such as a pressure
sensitive adhesive. U.S. Pat. No. 5,357,007 describes mixing spray
dried MQ resin with a fluid network mixture of an alkenyl siloxane,
a silicon hydride siloxane and a hydrosilylation catalyst to form a
pressure sensitive adhesive.
U.S. Pat. No. 8,017,712 describes producing a solid solventless MQ
resin by feeding a MQ resin dispersed in a volatile solvent into an
extruder, removing the volatile solvent and recovering the extruded
solid solventless MQ resin.
A volatile compound is a compound which is easily evaporated at
room temperature (20-25.degree. C.). A volatile compound has a high
vapor pressure at ordinary room temperature. A volatile compound
has a low boiling point, typically less than or equal to
250.degree. C. measured at a standard atmospheric pressure.
DETAILED DESCRIPTION OF THE INVENTION
A process according to the present invention for the production of
a pressure sensitive adhesive comprises dissolving a particulate
solid MQ silicone resin having a bulk density in the range 0.4-0.9
g/cm.sup.3 in a volatile solvent, and dissolving a
polydiorganosiloxane having a viscosity of 0.1 to 40,000 Pas at
25.degree. C. in the volatile solvent before, simultaneously with
or after dissolving the solid MQ silicone resin.
The particulate solid MQ silicone resin having a bulk density in
the range 0.4-0.9 g/cm.sup.3 can be produced by the process
described in U.S. Pat. No. 8,017,712, which is hereby incorporated
by reference. Thus the process of the invention according to one
aspect includes the initial step of producing the particulate solid
MQ silicone resin having a bulk density in the range 0.4-0.9
g/cm.sup.3 by feeding at least one MQ silicone resin dispersed in a
volatile solvent into an extruder, removing the volatile solvent in
the extruder to form a solid solventless MQ silicone resin,
extruding the solid solventless MQ silicone resin, and comminuting
the extruded solid solventless MQ silicone resin.
The extruder is generally a devolatilizing extruder capable of
heating the MQ silicone resin, removing volatiles under reduced
pressure and moving highly viscous molten materials and solid
materials through the process steps. Examples of useful extruders
include single screw or twin screw extruders. Typically a
twin-screw extruder is used. The conditions of extrusion are for
example as described in U.S. Pat. No. 8,017,712.
The solid solventless MQ silicone resin produced by the above
process is generally friable when cooled to ambient temperature and
can readily be comminuted under any type of strain to form flakes.
Cooling may be augmented by passing the extruded densified stream
through a water bath or spray. The solid solventless MQ silicone
resin can be extruded onto an ice chilled drum to rapidly cool and
flake the resin. The solid solventless MQ silicone resin can
alternatively be comminuted into chunks or pellets upon exiting the
extrusion device.
The MQ silicone resin can in general be any polymer comprised
primarily of R.sub.3SiO.sub.1/2 and SiO.sub.4/2 units. The MQ
silicone resin may optionally contain up to 20 mole %
R.sub.2SiO.sub.2/2 and/or RSiO.sub.3/2 units wherein each R is a
functional or non-functional, substituted or unsubstituted
monovalent radical. The MQ silicone resin can for example be of the
general formula R.sup.1.sub.n(R.sup.2O).sub.bSiO.sub.(4-n-b/2),
where each R.sup.1 is monovalent and independently selected from
hydrogen, alkyl, alkenyl, oximo, aryl, carbinol, anhydride, epoxy,
carboxyl, ether, polyether, amide, and alkyl amino groups, which
R.sup.1 groups may be the same or different, with the proviso that
at least 60 mole percent of R.sup.1 groups are methyl, each R.sup.2
is hydrogen or a monovalent alkyl group having 1 to 4 carbon atoms,
n has an average value from 1.1 to 1.6, and b is such that group
(R.sup.2O) is 0 to 10 weight percent of the MQ resin.
The MQ silicone resin can for example have a number average
molecular weight (Mn) of at least 1,000 or 1,500 up to 20,000 or
30,000. Often the MQ silicone resin has Mn between 1,500 and 7,500,
alternatively between 2,000 and 5,000.
The MQ silicone resin can contain functional groups, which may be
chosen to be reactive with functional groups in the
polydiorganosiloxane. Thus for use with a hydroxyl-terminated
polydiorganosiloxane having Si--OH functional groups, the MQ
silicone resin can contain silicon-bonded hydroxyl or alkoxy
groups. For example the MQ silicone resin can have the general
formula R.sup.1.sub.n(R.sup.2O).sub.bSiO.sub.(4-n-b/2), where
R.sup.1, R.sup.2 and n are defined as above and b is such that
group (R.sup.2O) is 1 to 10 weight percent of the MQ resin.
For use with an alkenyl-functional polydiorganosiloxane, the MQ
silicone resin can contain silicon-bonded alkenyl groups such as
for example vinyl groups. Such a MQ silicone resin may also contain
R.sup.2O groups or may be a capped resin containing no
silicon-bonded hydroxyl or alkoxy groups.
MQ resins are usually produced in dispersion in an aromatic
hydrocarbon solvent such as toluene or xylene. Thus in the initial
step of producing the particulate solid MQ silicone resin having a
bulk density in the range 0.4-0.9 g/cm.sup.3 by feeding at least
one MQ silicone resin dispersed in a volatile solvent into an
extruder, the volatile solvent in which the MQ silicone resin is
dispersed is usually an aromatic hydrocarbon.
In some instances, it may be preferred to avoid pressure sensitive
adhesives compositions containing aromatic hydrocarbon solvents for
different reasons for example for regulatory reasons.
In some embodiments, the volatile solvent used in the present
invention is substantially free of one or more of xylene, toluene,
ethyl benzene because of toxicity concerns associated to these
compounds. In some embodiments, volatile solvent used in the
present invention is substantially free of aromatic hydrocarbon
solvent.
The volatile solvent into which the particulate solid MQ silicone
resin is dissolved can for example be an aliphatic hydrocarbon, a
volatile silicone solvent, an ester, a ketone, an ether or even an
aromatic hydrocarbon.
Examples of suitable aliphatic hydrocarbons include linear,
branched or cyclic aliphatic hydrocarbons having 6 to 16 carbon
atoms, for example saturated acyclic aliphatic hydrocarbons
(paraffins) such as heptane, hexane, octane, isooctane, decane,
isodecane, isohexadecane or dodecane or isododecane and cyclic
aliphatic hydrocarbons such as cyclohexane, methylcyclohexane or
decahydronaphthalene. The aliphatic hydrocarbon solvent can be an
alkene, for example heptene, cyclohexadiene, cyclohexene, or
2,5-dimethyl-2,4-hexadiene. Mixtures of aliphatic hydrocarbons are
also suitable, for example the mixture of branched paraffins sold
under the trade mark ISOPAR.RTM..
In some embodiments, the volatile solvent is heptane or a volatile
silicone solvent. Heptane is preferred.
Examples of suitable volatile silicone solvents include linear,
branched and cyclic polydiorganosiloxanes, for example
polydimethylsiloxanes such as linear trimethylsilyl-terminated
polydimethylsiloxanes having a viscosity of 0.65 to 5 mPas at
25.degree. C., and cyclic polydimethylsiloxanes such as
decamethylcyclopentasiloxane and octamethylcyclotetrasiloxane.
Volatile silicone solvents can contain organic groups other than
methyl, for example higher alkyl groups or phenyl groups. An
example is 3-octyl heptamethyl trisiloxane.
Examples of suitable ester solvents are carboxylate esters such as
alkyl carboxylate esters and carbonate esters such as alkyl
carbonate esters. For example the volatile solvent can comprise at
least one C.sub.1-8 alkyl ester of a C.sub.2-4 carboxylic acid such
as ethyl acetate or butyl acetate. Examples of suitable carbonate
ester solvents include diethyl carbonate and dicaprylyl
carbonate.
Examples of suitable ketone solvents include methyl isobutyl ketone
(4-methyl-2-pentanone), 2-pentanone, 3-hexanone and methyl isoamyl
ketone (5-methyl-2-hexanone).
Examples of suitable ether solvents include dibutyl ether, volatile
polyethers such as 1-(propoxymethoxy)propane and cyclic ethers such
as cyclopentamethyl ether.
Examples of volatile aromatic hydrocarbons into which the
particulate solid MQ silicone resin is dissolved include toluene,
xylene and benzene. For example the MQ silicone resin may have been
prepared in a technical grade of xylene containing a low level of
ethylbenzene. For most uses this is acceptable, but for some uses
such as medical pressure sensitive adhesives it may be advantageous
to re-dissolve the MQ silicone resin in toluene. Alternatively the
MQ silicone resin may have been prepared in toluene but xylene may
be preferred as the pressure sensitive adhesive solvent because of
its higher flash point. The polydiorganosiloxane which is dissolved
in the volatile solvent when producing the pressure sensitive
adhesive is a liquid polydiorganosiloxane having a viscosity of 0.1
to 40,000 Pas at 25.degree. C. The polydiorganosiloxane is
dissolved in the volatile solvent before, simultaneously with or
after dissolving the solid MQ silicone resin. Conveniently, for
example the solid MQ silicone resin is dissolved in the volatile
solvent and the polydiorganosiloxane is dissolved in the resulting
solution. The weight ratio of MQ silicone resin to
polydiorganosiloxane can for example be in the range 0.5:1 to
4:1.
The polydiorganosiloxane can contain groups reactive with
functional groups present in the MQ silicone resin. For example,
the polydiorganosiloxane can contain silicon-bonded hydroxyl groups
which are reactive with silicon-bonded hydroxyl or alkoxy groups in
the MQ silicone resin. The polydiorganosiloxane can for example be
a hydroxyl-terminated polydiorganosiloxane.
A catalyst for reaction of the functional groups of the
polydiorganosiloxane with functional groups present in the MQ
silicone resin, and/or a cross-linking agent for reacting together
the polydiorganosiloxane and the MQ silicone resin, can be
dissolved in the volatile solvent before, simultaneously with or
after dissolving the solid MQ silicone resin and before,
simultaneously with or after dissolving the polydiorganosiloxane.
For example, if the polydiorganosiloxane contains silicon-bonded
hydroxyl groups and the MQ silicone resin contains silicon-bonded
hydroxyl or alkoxy groups, a catalyst for siloxane condensation of
the polydiorganosiloxane and the MQ silicone resin can be dissolved
in the volatile solvent when producing the pressure sensitive
adhesive.
The condensation catalyst can for example be an acid catalyst or a
base catalyst. Acid catalysts include carboxylic acids such as
acetic acid, benzoic acid, propanoic acid, butanoic acid, formic
acid and metal salts of carboxylic acids wherein the metal is
selected from the group consisting of Li, Na, K, Ce, and Ca, for
example potassium formate or potassium acetate.
A base catalyst can for example be selected from alkali metal
oxides, alkali metal alkoxides, alkali metal hydroxides, alkali
metal silanolates, alkali metal siloxanolates, alkali metal amides,
alkyl metals, ammonia, amines, and ammonia compounds such as
ammonium hydroxide and substituted ammonium hydroxides. Alkali
metal oxides are exemplified by sodium oxide. Alkali metal
alkoxides are exemplified by potassium ethoxide, sodium methoxide,
lithium methoxide, and potassium isopropoxide. Alkali metal
hydroxides are exemplified by potassium hydroxide, lithium
hydroxide, sodium hydroxide, and cesium hydroxide. Alkali metal
silanolates are exemplified by potassium silanolate, lithium
silanolate, and sodium silanolate. Alkali metal siloxanolates are
exemplified by potassium siloxanolate, lithium siloxanolate, and
sodium siloxanolate. Alkali metal amides are exemplified by sodium
amide and potassium amide. Alkyl metals are exemplified by
butyllithium. Amines are exemplified by triethylamine. Substituted
ammonium hydroxides are exemplified by quaternary ammonium
hydroxides such as tetramethyl ammonium hydroxide. The base
catalyst can alternatively be a quaternary phosphonium hydroxide
exemplified by tetrabutyl phosphonium hydroxide. The base catalyst
can alternatively be a salt of a strong base and weak acid such as
potassium carbonate.
A simple form of pressure sensitive adhesive comprises the MQ
silicone resin, the polydiorganosiloxane, and preferably a
condensation catalyst, all dissolved in the volatile solvent. The
pressure sensitive adhesive becomes tacky when exposed or applied
to a substrate so that the volatile solvent is able to evaporate.
Alternatively a polydiorganosiloxane containing silicon-bonded
hydroxyl groups and a MQ silicone resin containing silicon-bonded
hydroxyl or alkoxy groups, and preferably a condensation catalyst,
can be reacted when dissolved in the volatile solvent to produce a
`bodied` pressure sensitive adhesive. The solution of the MQ
silicone resin, the polydiorganosiloxane and a condensation
catalyst can for example be heated at a temperature in the range
50.degree. C. to 200.degree. C.
The polydiorganosiloxane can alternatively be an alkenyl-functional
polydiorganosiloxane containing silicon-bonded alkenyl groups for
example vinyl or hexenyl groups. The polydiorganosiloxane can
contain alkenyl terminal groups, for example a
dimethylvinylsilyl-terminated polydimethylsiloxane, and/or pendant
Si-bonded alkenyl groups. For example, the polydiorganosiloxane can
contain trimethylsiloxy-terminated
polydimethylsiloxane-polymethylvinylsiloxane copolymers,
vinyldimethylsiloxy-terminated
polydimethylsiloxane-polymethylvinylsiloxane copolymers,
trimethylsiloxy-terminated
polydimethylsiloxane-polymethylhexenylsiloxane copolymers,
hexenyldimethylsiloxy-terminated
polydimethylsiloxane-polymethylhexenylsiloxane copolymers,
vinyldimethylsiloxy-terminated
polydimethylsiloxane-polymethyhexenylsiloxane copolymers,
trimethylsiloxy-terminated polymethylvinylsiloxane polymers,
trimethylsiloxy-terminated polymethylhexenylsiloxane polymers,
vinyldimethylsiloxy-terminated polydimethylsiloxane polymers, and
hexenyldimethylsiloxy-terminated polydimethylsiloxane polymers,
vinyldimethylsiloxy terminated
poly(dimethylsiloxane-monomethylsilsesquioxane) polymers,
vinyldimethylsiloxy terminated
poly(dimethylsiloxane-vinylmethylsiloxane-methylsilsesquioxane)
copolymers; trimethylsiloxy terminated
poly(dimethylsiloxane-vinylmethylsiloxane-methylsilsesquioxane)
polymers, hexenyldimethylsiloxy terminated
poly(dimethylsiloxane-monomethylsilsesquioxane) polymers,
hexenyldimethylsiloxy terminated
poly(dimethylsiloxane-hexenylmethylsiloxane-methylsilsesquioxane)
copolymers; trimethylsiloxy terminated
poly(dimethylsiloxane-hexenylmethylsiloxane-methylsilsesquioxane)
polymers, vinyldimethylsiloxy terminated
poly(dimethylsiloxane-silicate) copolymers,
hexenyldimethylsiloxy-terminated poly(dimethylsiloxane-silicate)
copolymers, trimethylsiloxy terminated
poly(dimethylsiloxane-vinylmethylsiloxane-silicate) copolymers and
trimethylsiloxy terminated
poly(dimethylsiloxane-hexenylmethylsiloxane-silicate) copolymers,
vinylsiloxy or hexenylsiloxy terminated
poly(dimethylsiloxane-hydrocarbyl copolymers), mixed
trimethylsiloxy-vinyldimethylsiloxy terminated
poly(dimethylsiloxane-silicate copolymers), mixed
trimethylsiloxy-hexenyldimethylsiloxy terminated
poly(dimethylsiloxane-silicate copolymers), mixed
trimethylsiloxy-vinyldimethylsiloxy terminated
poly(dimethylsiloxane-vinylmethylsiloxane-silicate) copolymers and
mixed trimethylsiloxy-hexenyldimethylsiloxy terminated
poly(dimethylsiloxane-hexenylmethylsiloxane-silicate) copolymers.
vinylsiloxy terminated or hexenylsiloxy terminated
poly(dimethylsiloxane-polyoxyalkylene) block copolymers,
alkenyloxydimethylsiloxy terminated polyisobutylene and
alkenyloxydimethylsiloxy terminated
polydimethylsiloxane-polyisobutylene block copolymers.
A pressure sensitive adhesive composition comprising an
alkenyl-functional polydiorganosiloxane often contains a
cross-linking agent containing Si--H groups, for example a Si--H
functional polysiloxane. The Si--H functional polysiloxane can be
exemplified by dimethylhydrogensiloxy-terminated
polydimethylsiloxane polymers, di methyl hydrogensiloxy-terminated
polymethylhydrogensiloxane polymers, di methyl
hydrogensiloxy-terminated
polydimethylsiloxane-polymethylhydrogensiloxane copolymers,
trimethylsiloxy-terminated
polydimethylsiloxane-polymethylhydrogensiloxane copolymers, or
trimethylsiloxy-terminated polymethylhydrogensiloxane polymers,
each having a degree of polymerization of from 5 to 100 and a
viscosity at 25.degree. C. of from 5 to 100
milliPascal-seconds.
A pressure sensitive adhesive composition comprising an
alkenyl-functional polydiorganosiloxane usually contains a
hydrosilylation catalyst such as a platinum group metal-containing
catalyst. By platinum group it is meant ruthenium, rhodium,
palladium, osmium, iridium and platinum and complexes thereof.
Platinum group metal-containing catalysts useful in preparing the
compositions of the present invention are the platinum complexes
prepared as described by Willing, U.S. Pat. No. 3,419,593, and
Brown et al, U.S. Pat. No. 5,175,325, each of which is hereby
incorporated by reference to show such complexes and their
preparation. Other examples of useful platinum group
metal-containing catalysts can be found in Lee et al., U.S. Pat.
No. 3,989,668; Chang et al., U.S. Pat. No. 5,036,117; Ashby, U.S.
Pat. No. 3,159,601; Lamoreaux, U.S. Pat. No. 3,220,972; Chalk et
al., U.S. Pat. No. 3,296,291; Modic, U.S. Pat. No. 3,516,946;
Karstedt, U.S. Pat. No. 3,814,730; and Chandra et al., U.S. Pat.
No. 3,928,629 all of which are hereby incorporated by reference to
show useful platinum group metal-containing catalysts and methods
for their preparation. The platinum-containing catalyst can be
platinum metal, platinum metal deposited on a carrier such as
silica gel or powdered charcoal, or a compound or complex of a
platinum group metal. Preferred platinum-containing catalysts
include chloroplatinic acid, either in hexahydrate form or
anhydrous form, and or a platinum-containing catalyst which is
obtained by a method comprising reacting chloroplatinic acid or
platinum dichloride with an aliphatically unsaturated organosilicon
compound such as divinyltetramethyldisiloxane, or
alkene-platinum-silyl complexes as described in U.S. Pat. No.
6,605,734, which is hereby incorporated by reference. The platinum
catalyst can for example be present in an amount sufficient to
provide 2 parts per million (ppm) to 200 ppm of platinum in the
pressure sensitive adhesive composition.
A pressure sensitive adhesive composition comprising an
alkenyl-functional polydiorganosiloxane may also comprise an
inhibitor that inhibits the catalytic activity of platinum group
metal-containing catalysts at room temperature but does not
interfere with the properties of the catalyst at elevated
temperatures. Examples of suitable inhibitors include ethylenically
or aromatically unsaturated amides, acetylenic compounds, silylated
acetylenic compounds, ethylenically unsaturated isocyanates,
olefinic siloxanes, unsaturated hydrocarbon monoesters and
diesters, conjugated ene-ynes, hydroperoxides, nitriles, and
diaziridines. Inhibitors are exemplified by
1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol,
2-phenyl-3-butyn-2-ol, 2-ethynyl-isopropanol,
2-ethynyl-butane-2-ol, and 3,5-dimethyl-1-hexyn-3-ol, silylated
acetylenic alcohols exemplified by
trimethyl(3,5-dimethyl-1-hexyn-3-oxy)silane,
dimethyl-bis-(3-methyl-1-butyn-oxy)silane,
methylvinylbis(3-methyl-1-butyn-3-oxy)silane, and
((1,1-dimethyl-2-propynyl)oxy)trimethylsilane, unsaturated
carboxylic esters exemplified by diallyl maleate, dimethyl maleate,
diethyl fumarate, diallyl fumarate, and
bis-2-methoxy-1-methylethylmaleate, mono-octylmaleate,
mono-isooctylmaleate, mono-allyl maleate, mono-methyl maleate,
mono-ethyl fumarate, mono-allyl fumarate, and
2-methoxy-1-methylethylmaleate; conjugated ene-ynes exemplified by
2-isobutyl-1-butene-3-yne, 3,5-dimethyl-3-hexene-1-yne,
3-methyl-3-pentene-1-yne, 3-methyl-3-hexene-1-yne,
1-ethynylcyclohexene, 3-ethyl-3-butene-1-yne, and
3-phenyl-3-butene-1-yne, and vinylcyclosiloxanes such as
1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane. Generally
when inhibitor is present to the composition, it will be present in
amounts from 0.05 to 1 weight percent of the pressure sensitive
adhesive composition.
The Si--H functional polysiloxane crosslinking agent and the
hydrosilylation catalyst, and the inhibitor if used, are dissolved
in the volatile solvent before, simultaneously with or after
dissolving the solid MQ silicone resin and before, simultaneously
with or after dissolving the polydiorganosiloxane.
The MQ silicone resin for use in a pressure sensitive adhesive
composition comprising an alkenyl-functional polydiorganosiloxane
may contain alkenyl groups so that the MQ silicone resin becomes
bonded to the polydiorganosiloxane through the Si--H functional
polysiloxane crosslinking agent upon curing, or may not contain
alkenyl groups.
The volatile solvent is preferably chosen to be unreactive under
the conditions used to prepare the pressure sensitive adhesive.
When producing a `bodied` pressure sensitive adhesive, the volatile
solvent is preferably chosen to be unreactive under the conditions
of the condensation reaction. We have found that ester solvents
such as ethyl acetate may undergo some hydrolysis when using a base
catalyst under the silicone condensation conditions described
above. Unsaturated hydrocarbon solvents may be avoided when the
pressure sensitive adhesive includes a Si--H functional
polysiloxane crosslinking agent and a hydrosilylation catalyst.
Preferably the volatile solvent used in the present invention is
substantially free of ester solvent for example free of ethyl
acetate.
A portion of the polydiorganosiloxane can be added to the MQ
silicone resin in the extruder, so that the particulate solid MQ
silicone resin produced by comminuting the extruded solid
solventless MQ silicone resin contains a minor proportion of
polydiorganosiloxane. We have found that capped MQ silicone resins
containing no silicon-bonded hydroxyl or alkoxy groups,
particularly capped MQ silicone resins of molecular weight Mn
20,000 or above, are difficult to process in an extruder. Addition
of a small proportion of polydiorganosiloxane makes such capped MQ
silicone resins more readily extrudable without adversely affecting
removal of solvent from the MQ silicone resin in the extruder. If
polydiorganosiloxane is added to the MQ silicone resin in the
extruder, the weight ratio of MQ silicone resin to
polydiorganosiloxane in the extruder, and hence the weight ratio of
MQ silicone resin to polydiorganosiloxane in the particulate solid
MQ silicone resin, is preferably at least 5:1, for example in the
range 5:1 to 50:1.
MQ silicone resins containing silicon-bonded hydroxyl or alkoxy
groups, even of molecular weight Mn 20,000 or more, can readily be
extruded as a solid MQ silicone resin without needing addition of
polydiorganosiloxane.
The process of the invention is usually carried out batch wise. The
process can alternatively be carried out in a continuous processing
mode using equipment such as a twin screw extruder in a continuous
flow through process. The particulate solid MQ silicone resin is
fed to the extruder using appropriate equipment for feeding solids.
The other components of the pressure sensitive adhesive (e.g.
polydiorganosiloxane, new solvent, and catalyst, and any other
additives) are fed subsequently to the extruder. The extruder for
the process of this invention should be capable of removing the
small amount of water generated from any reaction between the MQ
resin and the polydiorganosiloxane.
The particulate solid MQ silicone resins having a bulk density in
the range 0.4-0.9 g/cm.sup.3 produced in an extruder have
advantages when producing pressure sensitive adhesives, compared to
use of the spray dried MQ silicone resins described in prior
patents. The spray dried MQ silicone resins are very low density,
dusty powders which can form explosive mixtures in air. This makes
them more difficult to handle and increases the hazards associated
with handling them.
An additional benefit of the process of the present invention is
that the process of effectively stripping out the solvent from the
MQ silicone resin in the extruder also removes some of the lowest
molecular weight components of the MQ resins, for example the
neopentamer ((CH.sub.3).sub.3SiO).sub.4Si. These lowest molecular
weight, most volatile fractions of the MQ silicone resins may
vaporize from the pressure sensitive adhesive during cure and then
tend to accumulate in ovens and coating equipment as sticky
deposits and dust. Using the process of the present invention the
quantity of these undesirable resin fractions is reduced and
therefore the tendency to create deposits in the ovens of users of
the pressure sensitive adhesives during coating and curing is
reduced.
The pressure sensitive adhesive compositions produced according to
the invention can contain minor amounts of additives. For example
the composition may contain a stabiliser. The stabiliser may be a
silyl phosphate such as a monosilyl phosphate, a disilyl phosphate,
or a trisilyl phosphate or a rare earth metal salt of a fatty acid.
Examples of silyl phosphates include trimethylsilyl dihydrogen
phosphate, bis(trimethylsilyl)hydrogen phosphate,
tris(trimethylsilyl)phosphate, or a combination thereof. Examples
of suitable silyl phosphates are disclosed in U.S. Pat. No.
5,041,586, which is hereby incorporated by reference. Examples of
rare earth metals suitable for forming the fatty acid salt include,
cerium, lanthanum and praseodymium with cerium being typical. The
fatty acid generally contains 6 to 18 carbon atoms with 8 carbon
atoms such as 2-ethylhexanoic acid being typical. The typical salt
is cerium octoate. The amount of stabiliser may range from 0 to
1000 parts per million by weight of the pressure sensitive adhesive
composition, typically 10 to 300 parts per million.
The silicone pressure sensitive adhesives prepared by the method of
this invention will readily stick to support a solid support or
substrate, whether flexible or rigid. These pressure sensitive
adhesive compositions may be applied to a surface by any suitable
means such as rolling, spreading or spraying. The surface of the
support and the substrate to which the support is adhered may be
any known solid material such as metals, paper, wood, leather,
fabrics, organic polymeric materials, painted surfaces, siliceous
materials such as concrete, bricks, cinderblocks, and glass
including glass cloth. After applying it to the surface, the
adhesive may be cured by air drying or heating for example at
temperatures of up to 300.degree. C.
Useful articles which can be prepared with the silicone pressure
sensitive adhesives of this invention include pressure sensitive
tapes, labels, emblems and other decorative or informational
signs.
EXAMPLES
The invention is illustrated by the following Examples, in which
parts and percentages are by weight.
Comparative Example C1
To a 1 liter, three-neck flask, equipped with a stirrer and
condenser with Dean-Stark water trap, 325.9 gm of a MQ silicone
resin of empirical formula M.sub.0.95Q or
(CH3).sub.n(HO).sub.bSiO.sub.(4-n-b/2), where n=1.46, Mn=2350, and
OH content is 2.5% as delivered in xylene (71.8% resin in xylene)
was added followed by 148.2 gm of xylene. With stirring 126.0 gm of
hydroxyl-endblocked polydimethylsiloxane fluid having a viscosity
of about 55 Pas and Mn 52,910 was added to the flask. A tube was
lowered below the liquid level and ammonia was bubbled into the
mixture while stirring continued. The flask was heated to
115.degree. C. and held for two hours with the ammonia bubbling and
stirring continuing. After two hours, 1.1 ml of water was observed
in the trap. The ammonia was stopped and the flask was heated to
135.degree. C. Nitrogen was bubbled through the mixture and the
mixture was tested with pH paper until it showed a neutral pH. The
resulting pressure sensitive adhesive was cooled and poured out of
the flask.
Example 1
This Example describes dissolving in xylene a solventless solid MQ
silicone resin prepared from a xylene solution of the MQ resin.
A solventless solid MQ silicone resin was prepared from the MQ
silicone resin in xylene solution described in the Comparative
Example using the conditions described in Example 1 of U.S. Pat.
No. 8,017,712. To a 1/2 gallon jar, 980.06 gm of solid MQ resin was
added followed by 420.51 gm of xylene. The jar was mixed and the MQ
resin was allowed to dissolve.
To a 1 liter, three-neck flask, equipped with a stirrer and
condenser with Dean-Stark water trap, 335.5 gm of the solution
prepared above was added followed by 138.7 gm of xylene. With
stirring 126.0 gm of a hydroxyl-endblocked polydimethylsiloxane
exhibiting a viscosity of approximately 50,000 mPas at 25.degree.
C. was added to the flask. A tube was lowered below the liquid
level and ammonia was bubbled into the mixture while stirring
continued. The flask was heated to 115.degree. C. and held for two
hours with the ammonia bubbling and stirring continuing. After two
hours, 2.0 ml of water was observed in the trap. The ammonia was
stopped and the flask was heated to 135.degree. C. Nitrogen was
bubbled through the mixture and the mixture was tested with pH
paper until it showed a neutral pH. The resulting pressure
sensitive adhesive was cooled and poured out of the flask.
Example 2
To a 1/2 gallon jar, 297.62 gm of the solid MQ resin described in
Example 1 was added followed by 198.45 gm of heptane. The jar was
mixed and the MQ resin was allowed to dissolve.
To a 1 liter, three-neck flask, equipped with a stirrer and
condenser with Dean-Stark water trap, 389.8 gm of the solution
prepared above was added followed by 84.5 gm of heptane. With
stirring 126.0 gm of a hydroxyl-endblocked polydimethylsiloxane
exhibiting a viscosity of approximately 50,000 mPas at 25.degree.
C. was added to the flask. A tube was lowered below the liquid
level and ammonia was bubbled into the mixture while stirring
continued. The flask was heated to 90.degree. C. and held for two
hours with the ammonia bubbling and stirring continuing. After two
hours, 1.0 ml water was observed in the trap. The ammonia was
stopped and the flask was heated to 92.degree. C. Nitrogen was
bubbled through the mixture and the mixture was tested with pH
paper until it showed a neutral pH. The resulting pressure
sensitive adhesive was cooled and poured out of the flask.
Test results from Examples 1 and 2 and the Comparative Example are
shown in Table 1. The viscosity of each pressure sensitive
adhesive, adjusted to 60% solids, was measured at 25.degree. C.
The samples for testing were prepared as follows: Pressure
sensitive adhesive laminates were prepared by casting the solvated
adhesives onto 2-mil (50 .mu.m) thick polyester (PET) films using a
vacuum coating table with an appropriate application bar to yield a
1.0-mil (25 .mu.m) dry pressure sensitive adhesive thickness. The
vacuum plate was turned on and set to 15'' of vacuum. The substrate
to be coated was placed on the plate and the vacuum held it firmly
in place. The application bar was placed at the top of the
substrate and a puddle of adhesive was poured in front of the bar.
The bar was pulled down the substrate at a constant speed and
pressure. The laminate was placed in an air-circulating oven and
dried at 110.degree. C. for 6 minutes to remove all solvent. Once
dried, the laminate was allowed to cool to ambient temperature and
placed in a sample box to protect from contamination prior to
testing.
Each prepared laminate was cut into test strips using a 1 inch (25
mm) specimen tape cutter. A cutting board was placed under the
laminate and the cutter was run in the same direction as the
application bar. Each laminate provided 4 test strips.
Laminate thickness was measured using a DIGIT-MIKE.RTM. plus
micrometer. The micrometer was zeroed by initially measuring the
thickness of two pieces of test substrate. A piece of the pressure
sensitive adhesive laminate was cut with the specimen cutter and
covered with a second piece of test substrate. Measurements were
taken in at least three places on the new laminate where adhesive
was present to ensure the desired pressure sensitive adhesive
thickness was obtained throughout the sample.
The peel adhesion (180.degree.) was tested according to ASTM D3330
and PSTC-1 standards. All tests were conducted on an Instron
tensile tester at a peel rate of 12 inches (300 mm) per minute with
2.0 mil (50 .mu.m) PET as the test substrate. A 1 inch wide sample
strip of PSA was adhered to a clean stainless steel panel using a 2
kg roller with 2 passes. Samples were allowed 20 minutes to
equilibrate at room temperature before performing the tests. The
average of 3 measurements was typically reported.
The static shear strength was measured according to ASTM D3654 and
PSTC-7 standards. Samples were prepared for testing by placing a
1-inch wide strip of PSA onto a clean stainless steel test panel.
The samples were cut to provide a 1 inch by 1 inch area of contact
and secured with 2 passes of a 2 kg roller. Metal hangers were
secured from the bottom of each test strip and reinforced to ensure
that failure of the sample occurred at the testing interface. Each
test sample was placed in the ChemInstruments HT-8 Shear Bank
testing apparatus and the timer was reset to zero. A 4 pound (1.8
kg) weight was hung from each sample and the time to failure was
recorded as the sample fell off the panel. The average of 3
measurements was typically reported.
The TA-Total Area and TA-Area Ratio were measured as follows:
Testing with the Texture Analyzer TA.XT2 sold by Texture
Technologies Corp. was completed using a 7 mm, stainless steel
punch probe with a 1-inch radius of curvature. Using 10-mil PET as
the testing substrate, samples were placed under an indexable brass
plate to position them for analysis. The following program settings
were used: Pre-test speed: 0.5 mm/sec Test speed: 0.2 mm/sec
Post-test speed: 0.2 mm/sec Test force: 100 grams Dwell time: 0.5
seconds Trigger force: 1.0 gram Trigger mode: Auto Collection rate:
200 points/second
A software macro was run after the completion of each sample to
calculate the Peak Force, Area 1:2, Area 2:3, Total Area, and Area
Ratio based on three points on the graph. Point 1 is where the
actual graph begins to cross over the x-axis into a positive force
region. Point 2 is where the graph reaches its maximum force. Point
3 is where the graph returns to the x-axis. Area 1:2 is the area
under the curve from points 1 to 2, Area 2:3 is the area under the
curve from points 2 to 3, the Total Area is the area under the
curve from points 1 to 3, and the Area Ratio is calculated by
dividing Area 2:3 by Area 1:2. The average of 5 measurements was
typically reported. The Total Area is a measure of the amount of
work required to pull a probe free from the adhesive, and the Area
Ratio corresponds to the tackiness of the adhesive.
TABLE-US-00001 TABLE 1 Example Control (C1) 1 2 Resin Control Solid
Solid Solvent Xylene Xylene Heptane Viscosity @ 60% (cP) 708 753
726 Peel Adhesion (N/10 mm) 9.94 10.14 8.3 Static Shear (hours)
171.2 163.7 163.6 TA - Total Area (g sec) 30.3 30.43 19.44 TA -
Area Ratio 0.2 0.15 0.15
The test results in Table 1 show that the control C1 and Example 1
prepared from the solid MQ resin dissolved in xylene provided very
similar results, indicating that producing the MQ silicone resin in
particulate solid form and re-dissolving it did not deleteriously
affect the pressure sensitive adhesive. Example 2 prepared from the
solid MQ resin dissolved in heptane also provided similar results
and produced an acceptable pressure sensitive adhesive.
Example 3
To a 2 liter, three-neck flask, equipped with a stirrer and
condenser with Dean-Stark water trap, 493.71 gm of xylene was
added. With stirring, 372.88 gm of the solid MQ resin described in
Example 1 was added. With continued stirring, 309.21 gm of
hydroxyl-endblocked polydimethylsiloxane gum exhibiting a Mn of
approximately 300,000 Daltons was added in small pieces and 1.24 gm
of silyl phosphate was added. The mixture was stirred overnight to
assure the silicone fluid was fully dissolved. A mixture of 2.4017
gm benzoic acid and 21.5992 gm of xylene was added. The entire
mixture was heated to the refluxing temperature of the xylene
(approximately 140.degree. C.) and held for 2.5 hours. The flask
was cooled and the resulting pressure sensitive adhesive was found
to exhibit 58.62% non-volatile content and viscosity of 31,800
mPas.
Samples for testing were prepared by the following procedure. Weigh
out at least 25 grams of adhesive. Using a freshly prepared
solution of 10% benzoyl peroxide (Lucidol 98) in Toluene, add 2%
(based on adhesive solids) benzoyl peroxide to the adhesive. Dilute
to 50+/-0.5% with toluene and mix for at least one minute. Apply
adhesive to a sheet of 1 mil (25 .mu.m) thick Mylar PET with an
automated coater so the final thickness after curing is 1.5-2.0
mils (37-50 .mu.m). Cure the adhesive for 2 minutes at 70.degree.
C. and then 2 minutes at 178.degree. C. Cut three 1 inch strips of
adhesive and apply each to a clean steel panel at a rate of 12
inches/minute with automated roll down instrument or using a 4.5
pound (2 kg) Hand Roller.
For adhesion testing, pull the strip from the steel in a direction
parallel with the steel plate. Measure the force of the pull and
record in ounces per inch. Report the average of the three pulls of
adhesive from the steel.
For tack, use an instrument equivalent to a POLYKEN.TM. Probe Tack
Tester--Model PT-1000--ChemInstruments, Inc. Place 5 annular rings
in a row on a 1 inch strip on film prepared as described above for
adhesion. Separate the rings from each other by cutting the film
between them. Place the annular ring on the three set screws on the
test platform. Press the START toggle button for two seconds and
release it to start the test sequence. The test platform will lower
until the probe contacts the tape for one second and then rise back
to the starting position. The tack value will be displayed. Report
the Maximum Force in grams.
The adhesion was 32.1 oz/in (365 g/cm) and the tack was 813 g as
measured by the methods described above, which were typical values
for a pressure sensitive adhesive prepared using the xylene
solution from which the solid MQ resin was prepared.
Example 4
To a 500 ml three-neck flask, equipped with a stirrer and condenser
with Dean-Stark water trap, 129.21 g toluene was added. The
Dean-Stark trap was filled with toluene and a slow nitrogen purge
was used in the three neck flask. A total of 89.93 gm of the solid
MQ Resin described in Example 1 was added with 0.37 gm of a
solution of 10% silyl phosphate in toluene. The stirrer was turned
on at 200 RPM. Small balls of the silicone gum described in Example
3 were added until a total of 79.98 gm had been added. The stirring
continued for approximately 2 hours and 45 minutes and then was
shut off over night. The next morning the stirrer was turned on
again and the flask was heated to the reflux temperature of the
toluene. It was held at reflux for 1 hour and 42 minutes and then
the reflux stopped for 25 minutes. The reflux was restarted and
continued for 1 hour and 56 minutes. The flask was allowed to cool
and the resulting pressure sensitive adhesive was poured out. The
adhesion and tack were measured as described in Example 3 with the
following differences. The adhesive was coated on 2 mil (50
.mu.m)PET using 3 mil (75 .mu.m) bird bar, and curing was at
80.degree. C. for 2 minutes and then 180.degree. C. for 2 minutes.
The pressure sensitive adhesive exhibited values of Adhesion=47.9
oz/in (544 g/cm) and Tack=856 g.
Example 5
To a 500 ml three-neck flask, equipped with a stirrer and condenser
with Dean-Stark water trap, 129.23 gm of toluene was added. The
Dean-Stark trap was filled with toluene and a slow nitrogen purge
was used in the three neck flask. A total of 93.50 gm of the solid
MQ Resin described in Example 1 was added with 0.37 gm of a
solution of 10% silyl phosphate in toluene. The stirrer was turned
on at 200 RPM. Small balls of the silicone gum described in Example
3 were added until a total of 76.39 gm had been added. The stirring
continued for approximately 2 hours and 15 minutes and then was
shut off over night. The next morning the stirrer was turned on
again and the flask was heated to the reflux temperature of the
toluene. It was held at reflux for 4 hours. The flask was allowed
to cool and the resulting pressure sensitive adhesive was poured
out. The adhesion and tack were measured as described in Example 4
The pressure sensitive adhesive exhibited values of Adhesion=51.9
oz/in (590 g/cm) and Tack=897 g.
Example 6
In preparation for the run, 46.8 kg of the solid MQ Resin described
in Example 1 was added to a 55 gallon drum, then 62.5 kg of toluene
was added to the drum and this mixture was drum tumbled for 6
hours. The kettle was cleaned by boiling toluene and at the end of
the last boil-up of toluene the trap was left full of toluene so
that the kettle could be refluxed without changing the toluene
concentration in the kettle.
The 109.3 kg of MQ resin dissolved in toluene was added to a 50
gallon glass lined kettle, equipped with an agitator, water trap,
and recycle loop. After loading, the agitator was started and set
to 200 rpm. While stirring, 35.3 kg of the silicone gum described
in Example 3 was loaded into the kettle via the hand hole. The gum
was cut into smaller pieces using a gum knife while loading. 17.40
grams of a mixture of Bis(Trimethylsilyl) Hydrogen Phosphate,
Trimethylsilyl Dihydrogen Phosphate, and
Tris(Trimethylsilyl)Phosphate was added to a glass bottle. To that
glass bottle, 156.62 grams of toluene was added. The mixture was
shaken and then added to the kettle via the hand hole. A nitrogen
purge was kept on the kettle throughout the entire raw material
loading process. The mixture in the kettle was allowed to mix for 2
hours while agitating at 200 rpm.
After blending, 253.89 grams of benzoic acid USP grade was loaded
into the kettle via the catalyst adder. The catalyst adder was
rinsed with 876 grams of toluene to make sure all of the benzoic
acid reached the kettle contents. The kettle was then heated to the
refluxing temperature of the toluene (approximately 111.degree. C.)
and held for 4 hours. A small amount of water was collected in the
trap. The kettle contents were cooled to 50.degree. C., and then
filtered through a 50 micron filter bag. The resulting pressure
sensitive adhesive was found to exhibit 56.22% non-volatile content
and a viscosity of 45,800 mPas.
The adhesion and tack were measured as described in Example 4. The
adhesion was 51 oz/in (580 g/cm) and the tack was 689 g which are
typical values for a bodied pressure sensitive adhesive produced
from the same raw materials using a silicone MQ resin as prepared
in xylene.
The present invention has been described herein in an illustrative
manner, and it is to be understood that the terminology which has
been used is intended to be in the nature of words of description
rather than of limitation. Many modifications and variations of the
present invention are possible in light of the above teachings. The
present invention may be practiced otherwise than as specifically
described within the scope of the appended claims. The subject
matter of all combinations of independent and dependent claims,
both single and multiple dependent, is herein expressly
contemplated.
* * * * *